The present invention relates generally to fasteners and more particularly to a metal piercing fastener for securing one or more metal/non-metal layers to at least one metal layer and retaining the secured layers in their positions permanently under adverse conditions.
Many fastener designs exist in the prior art and generally these designs can be placed into two different categories. The first are fasteners used in an environment where the fastener is accessible from both sides of the work pieces being joined together, which include traditional nut and bolt or the like. The other group or category of fasteners are those which must operate in environments wherein the fastener is usually only accessible from one side of the work pieces and may be manipulated from one and only one of its ends to accomplish its fastening task. This is called xe2x80x9cblindxe2x80x9d fastening and the present invention is directed to fasteners in this category.
In this latter category, there are many varieties of such fasteners. Traditional examples of such fasteners, including those capable of penetrating sheet metal, can be grouped into two categories. The first grouping consists of self-piercing and self-drilling threaded screws. The second grouping consists of brads, staples, nails, drive pins and the like. In the first group of fastening devices, a high rpm electric screw gun is usually used for installation. In the second grouping, a pneumatically actuated tool is normally utilized to cause the fastener to penetrate the work pieces and secure them together. In many instances where U-shaped, staple-like fasteners, brads, nails, drive pins, and the like have been employed, such fasteners are provided in an elongated continuous member or xe2x80x98stickxe2x80x99 with the penetrating points all facing in a common direction. These sticks are inserted into the magazine of a tool. The tool is placed at a desirable position over one of the work pieces being fastened to the other, is activated and a driving element is forcibly driven against the end of the fastener on the end opposite the point driving the fastening element through the work pieces to secure the same together.
In the case wherein a metal self-piercing screw is utilized, the screw is secured into the end of a power-driven rotating chuck attached to an electric screw gun. The tool, upon being activated, rapidly rotates the screw at approximately 2500 to 4000 rpm. Upon application of significant physical force by the installer, the rotational friction of the screw against the work piece heats the metal to a softened state thereby allowing penetration of the work piece. The helical threads engage the metal pulling the fastener through and securing the work pieces together. In the case wherein a metal self-drilling screw is utilized, it is secured into a similar tool as is used with self-piercing screws except this type of electric screw gun rotates the self-drilling screw at approximately 1800 to 2500 rpm. Also, similar to self-piercing screws, application of a significant force by the installer is required to press the cutting flutes into the metal to achieve a drilling operation. After a hole is drilled, the fastener then engages helical threads to secure the work pieces together.
With these examples of prior art, it should be noted that the threaded fastener advancement rate for the piercing or drilling operation is slower than the advancement rate when the fastener threads are engaged. This not only implies that these types of xe2x80x98blindxe2x80x99 fasteners have much slower installation rates and require considerable force to be applied by the operator but their self-piercing or self-drilling function must be completed before any of their threads become engaged within the substrates.
When a non-metal work piece is to be attached to a light-gauge metal substrate or two or more pieces of metal are to be attached, the bottom sheet may be pushed away from the top piece to be attached before the penetration and fastening process is completed. In the construction trades and fastener arts, this phenomenon is termed xe2x80x9coil canningxe2x80x9d. Fastener xe2x80x9coil canningxe2x80x9d is a function of fastener velocity, the metals"" deflection properties and the ratio of the substrate mass being displaced to the fastener mass. The current state of art utilizes helical threads to pull the two separated sheets together. The lack of some mode of clamping component within nails, drive pins or staples precludes such fasteners from successfully tightening substrates to light gauge metal(s) or two or more light gauge metals together. Prior art metal penetrating fasteners and particularly metal penetrating and self-drilling screws demonstrate various disadvantages. Significant training and installation experience is required to bring the installer skill to an acceptable level.
For example, when attaching a work piece such as drywall, it is important that the work piece not be damaged and be properly clamped to the metal stud substrate without overdriving the fastener crown into the workpiece or tearing the work piece paper laminate. Use of such screws is labor intensive and requires physical pressure against the installation tool, both of which contribute to worker fatigue. Another disadvantage of conventional self-piercing and self-drilling threaded fasteners is that their threads achieve contact with the thin sheet metal base substrate at only one or two relatively small contact areas along the slanting helical threads. A single thread only touches the material on one side and a twin-lead thread will have just two contact points. This small area of contact (deemed xe2x80x9cthread engagementxe2x80x9d) frequently contributes to a fastening failure mode referred to as xe2x80x9cthread strip-out.xe2x80x9d This can occur when a slight over-torqueing of the fastener causes this relatively small contact point in the metal to rapidly fatigue resulting in the destruction of the mechanical interlock between the thread and metal substrate. In addition, there is an industry trend towards the use of even thinner metals which will acerbate this problem.
With other conventional fasteners, such as nails, drive pins or staples, there is no effective device or means to provide a gripping and clamping action on the backside of the bottom substrate being fastened. Therefore, adequate clamping of sheets is not always assured. Even more lacking is their withdrawal or xe2x80x98pull-outxe2x80x99 resistant values that are dependent on lateral friction forces between the fastener""s contact points with the pierced holes. It has been determined that effective withdrawal or xe2x80x98pull-outxe2x80x99 values for these types of fasteners is not attained until the thickness of bottom substrate metal exceeds a thickness of 0.1250xe2x80x3 or that of a 11 gauge metal sheet. In addition, prior to the fastener of this invention, only drive pins within this category of blind fasteners have been able to consistently pierce metals of this thickness. The failure of these types of blind fasteners during severe conditions such as hurricanes, tornadoes, and earthquakes to effectively hold fastened substrates together has resulted in many of these types of fasteners being de-certified for light gauge structural metal construction applications. Additions of non-resilient spiral threads, flutes, undercuts, barbs or teeth to these products tend to only increase the physical dimensions of the substrate penetration pattern by ripping or removing the actual metal required to provide adequate clamping and holding.
Another consequence of this low thread-engagement condition is the lack of requisite friction to increase xe2x80x9cback-offxe2x80x9d resistance. When a threaded fastener is subjected to vibration or withdrawal stresses this xe2x80x9cback-offxe2x80x9d resistance is the force which keeps the fastener in place. In such thin materials and with such minor thread engagement, the xe2x80x9cback-offxe2x80x9d resistance is minimal and the fastener frequently becomes loose, thereby sacrificing the integrity of the fastened joint.
Furthermore, with conventional nails, staples, or drive pins designs, such fasteners lack an effective method to clamp two or more pieces of materials together where the bottom material is made of light gauge metal. During high velocity installation, the mass of these fastener bodies pushes the second or base material away from the top materials (this was previously referred above to as xe2x80x9coil-canning.xe2x80x9d) Even if these different types of fasteners manage to penetrate the base material, they have no effective design feature to pull or clamp the two or more sheets tightly together. Attempts have been made to incorporate xe2x80x9cspiralxe2x80x9d threads onto certain types of these fasteners. However, with the thin gauges of sheet metals in use, the xe2x80x9cspiralsxe2x80x9d achieve insufficient thread-engagement to function as an effective and consistent clamping mechanism. Additionally, when the fastener thread is already engaged in top sheets, subsequent sheets may be pushed away during initial penetration of the fastener. Basic mechanics disallow one xe2x80x9cspiralxe2x80x9d thread to pull against another thread on the same fastener. The result is that the metal sheets are not effectively clamped together.
Therefore, the need arises for a self-piercing fastener which may be fabricated from relatively thin, hardened and resilient material such as LGSM and which may be used with a power tool adapted to accommodate the fastener. The power tool user would require little or no training at all and would actuate the power tool by pulling a trigger, pushing a button or the like.
The need also arises for a novel fastener which may have a relatively low profile body equipped with a crown at one end and a piercing tip or point at the other end. Such a fastener should have high tensile and shear values as well as optimized gripping and clamping capability to provide high xe2x80x98withdrawalxe2x80x99 and xe2x80x98back-outxe2x80x99 resistant values. When the fastener is propelled, via a high velocity impact tool, it should be capable of effectively penetrating thin LGSM sheets with an insignificant occurrence of xe2x80x9coil canningxe2x80x9d. The fastener may be also provided with resilient gripping and clamping elements xe2x80x9ctinesxe2x80x9d which can be integrally formed from the fastener body. A resilient tine may be deflected into a void either within the body of the fastener or a void created elsewhere by the fastener""s penetration process. The deflection process may be invoked by a cam surface on that part of the tine, which will first contact the substrate or edges of the opening pierced by the fastener""s piercing tip. The process of deflecting the tine, with its protruding gripping and clamping elements, into these voids, ensures they will not enlarge or remove any additional LGSM substrate than was pierced or cut by the fastener""s tip/point. After passing through the LGSM substrate, the tine should be no longer restrained and capable of immediately attempting to spring-back to its original position. In doing so, it would move away from the fastener""s body and underneath the base material being fastened. The gripping and clamping elements may be opposed by at least one or more spring-loaded members including the fastener""s crown and driving stops on the fastener""s body to provide the spring-back force needed to push against the gripping and clamping elements thereby effectively securing the work pieces together over the expected lifetime of the fastener. Through appropriate formation of the piercing tip of the fastener, the pierced LGSM substrate should be left with a clean opening of diameter less than the diameter of the fastener locking element to effectively clamp the work pieces together. Such a fastener may be utilized in securing drywall to LGSM studs, plywood to LGSM studs, cement fibreboard to LGSM studs, or any other non-metal material to a metal material, or two or more layers of sheet metal together.
The present invention meets the above needs and is directed to a fastener for securing a plurality of laminar work pieces together, at least one of the laminar work pieces being metal, the fastener comprising: a metal body having a first end and a second end; a crown formed at the first end of the metal body, the crown adapted for clamping the plurality of laminar work pieces together; a metal piercing region formed at the second end of the metal body for piercing the plurality of laminar work pieces; and a gripping and clamping member disposed between the first and second ends of the metal body to lock the pierced laminar work pieces together.
In accordance with one aspect of the present invention, a metal piercing fastener is described for securing laminar work pieces together, one of which is metal, the fastener comprising a body formed from sheet spring metal material and having first and second ends and first and second side edges; a crown formed at the first end; a metal piercing region at the second end; the first and second side edges and the metal piercing region being coined; and a resilient locking member attached at one end thereof to the body intermediate the first and second ends.
In accordance with another aspect of the present invention, a metal piercing fastener for securing a first member to a second metal member, the fastener comprising a blade having first and second ends and first and second side edges formed from sheet spring material having a uniform thickness and a width substantially greater than the thickness; a crown protruding from the first end of the blade, the second end of the blade defining a metal penetrating region, the crown being adapted to receive an impact blow from a tool to drive the metal penetrating region through the second metal member; the blade defining a slot spaced inwardly from the first side edge and terminating adjacent the second end to provide a freestanding separate resilient tine extending upwardly from the second end of the blade and terminating intermediate the first and second ends, the tine having an inboard edge and on outboard edge; and a plurality of protruding elements formed on the outboard edge, each protruding element having a cam surface facing toward the second end for engaging the second metal member to urge the tine into the slot as the fastener passes through the metal workpiece.
In accordance with still another aspect of the present invention, a metal piercing fastener for securing a first member to a second metal member, the fastener comprising a blade having first and second ends and first and second side edges formed from sheet spring material having a non-uniform thickness and a width substantially greater than the thickness; a crown protruding from the first end of the blade, the second end of the blade defining a metal penetrating region, the crown being adapted to receive an impact blow from a tool to drive the metal penetrating region through the second metal member; the blade defining a slot spaced inwardly from the first side edge and terminating adjacent the second end to provide a freestanding separate resilient tine extending upwardly from the second end of the blade and terminating intermediate the first and second ends, the tine having an inboard edge and on outboard edge; and a plurality of protruding elements formed on the outboard edge, each protruding element having a cam surface facing toward the second end for engaging the second metal member to urge the tine into the slot as the fastener passes through the metal workpiece.
In accordance with yet another aspect of the present invention, a method for securing a plurality of laminar work pieces together, one of the laminar work pieces being metal, comprising the steps of providing a metal fastener body having a crown at one and a rigid metal piercing point at the other end; providing at least one resilient tine on the metal fastener body adapted for securely gripping and clamping the laminar work pieces during fastening; impacting the fastener crown with a tool to drive the fastener metal body into the plurality of laminar work pieces; and gripping and clamping the pierced laminar work pieces with the resilient tine to lock the pierced laminar work pieces together between the crown and the resilient tine.
In accordance with a different aspect of the present invention, fastener for securing an expanded wire to at least one laminar work piece, the fastener comprising a metal body having a first end and a second end; a crown formed at the first end of the metal body, the crown adapted for clamping the expanded wire to the at least one laminar work piece; a metal piercing region formed at the second end of the metal body for passing through the expanded wire and piercing the at least one laminar work piece; and a gripping and clamping member disposed between the first and second ends of the metal body to lock the expanded wire to the at least one pierced laminar work piece.
These and other aspects of the present invention will become apparent from a review of the accompanying drawings and the following detailed description of the preferred embodiments of the present invention.